The invention is based on a throttle device for a pressure control apparatus.
To regulate the pressure in a fuel supply system of an internal combustion engine, a pressure control apparatus that contains a pressure control valve is typically used. This valve is located on the compression side of a fuel pump that communicates with a tank. Some of the fuel pumped by the fuel pump is delivered to the engine via injection valves. In many internal combustion engines, one injection valve per cylinder is provided. The need is for the injection valves to inject the precise correct fuel quantity at any given moment, with only a very slight allowable deviation among the injection valves. The excess fuel quantity not needed by the engine is returned in the return line to the fuel tank via the pressure control valve. The pressure control valve regulates the pressure on the compression side of the fuel pump. In different motor vehicles, components are inserted into the return line leading back from the pressure control valve to the tank, in order to influence the return pressure. These components may for instance be a jet pump and/or a control valve. As such components, throttle devices which effect a throttling action by cross-sectional constriction have also already been proposed. This is in recognition of the fact that the noise produced by the pressure control valve and caused by the expansion of the fuel of the valve seat can be reduced by increasing the pressure in the return line. This reduces the pressure difference between the inflow line and the return line and thus reduces the noise produced. In known throttle devices, the throttling is achieved by means of a cross-sectional constriction in the return line. The flow cross section must be large enough that the return line pressure, if the flow rate is high, does not reach the inflow line pressure, in which case the control function would be lost. As a result, with a lesser flow rate there is a lesser return line pressure and hence a large pressure difference between the inflow and return lines. Because of a varying pressure difference between the inflow and return lines, a reduction in noise produced by the pressure control valve is hardly achievable.